In general, the amount of radioactivity of an atomic power plant or of a radioactive waste storage is smaller than that of daily or industrial waste, but since radioactivity has fatal possibility of radioactivity exposure, and a period for treating the same is long, safety in regard to the process of treating radioactivity has to be provided.
An atomic power plant or a radioactive waste storage is built as a concrete structure having multiple blocking walls in order to reduce the influence of radioactivity as much as possible. The blocking walls are formed as sealed containments by using, for example, cement having excellent heat resistance.
However, it has been recently revealed that a hangar which is regarded safe might also collapse under a certain condition, as the example of Japan which was damaged greatly by earthquakes and tsunamis showed. It showed that once a hangar collapses, a nuclear fuel rod is exposed in addition to exposure of radioactivity, and the critical problem of overheating is caused thereby. Moreover, although measures such as inputting cooling water to suppress the overheating of the nuclear fuel rod or inputting a boron solution in order to slow a nuclear reaction have been provided, there is the problem that these measures cost great manpower and vast economic losses.
Thus, the need arises for a structure that stores increasing radioactivity waste safely and thoroughly, and locally restricts the extent of collapse of a hangar even when a condition under which a containment is to necessarily collapse is created due to an earthquake or tsunami, and that delays leakage of radioactivity to thereby reduce the danger as much as possible.